This invention relates to an improved adjustable open-ended wrench.
One very common hardware item is the adjustable wrench in which an open-ended wrench has jaws with one of the jaws being movable toward the other jaw by rotating a thumbwheel. Another common tool serving a similar purpose is the wrench set, which includes a number of wrenches each having jaws of different dimensions. These tools typically allow an operator to loosen or tighten nuts of different sizes.
However, adjustable wrenches of the type having a rotatable thumb mechanism typically have a tendency to slip under load, particularly when the threaded mechanism becomes dirty and the wrench then becomes difficult to adjust. Slippage of such adjustable wrenches may result in damage to the nuts and bolts and possible injury to the operator.
The difficulty in using a number of wrenches of fixed dimension is apparent, in that it requires additional trouble to look through a set of wrenches to find the proper wrench to fit a particular nut. Often it is more convenient to simply use an adjustable wrench which has the difficulties mentioned above.
Many persons have attempted to design wrenches which can be adjusted to fit nuts of different sizes, but which do not require a thumb rotating mechanism. However, these variable wrenches typically have disadvantages which have prevented them from becoming popular in hardware stores.
For example, one type of prior art wrench has variable blades which may swing into place to vary the spacing between the jaws. Such a wrench is illustrated in U.S. Pat. Nos. 1,080,064, 1,399,966, 1,550,564 and 1,646,140. Among other things, the type of wrench having rotatable blades requires special provision for alignment of blades. Further, it may be possible to rotate one of the middle blades into the jaws without rotating other supportive blades and in this manner, damage to the blades may readily occur. Another type of adjustable wrench that has been designed in the prior art is a type in which a shim located adjacent each jaw can be slid into position to decrease the spacing between the jaws. This type of wrench is illustrated in U.S. Pat. Nos. 2,803,158, 2,900,857 and 3,738,203. One apparent disadvantage of this type of wrench is that there are only two usable shims with respect to each jaw opening and thus this type of wrench lacks the adjustability and versatility of other types of adjustable wrenches.
Another type of adjustable wrench is illustrated in U.S. Pat. No. 3,802,303. This type of adjustable wrench uses metallic inserts of prescribed dimensions which serve to vary the dimension of the jaw opening of the wrench. It is possible, however, that one or more of these metallic inserts may be lost because they are not a connected portion of the wrench itself. Further, by utilizing such inserts the wrench is unable to sustain the types of loads sustained by some other adjustable wrenches.
U.S. Pat. Nos. 1,204,433 and 1,529,605 show other types of adjustable wrenches, which are unduly complicated to manufacture and are believed not to be economically feasible.
An adjustable wrench using longitudinally slidable shims has been considered in U.S. Pat. Nos. 562,709 and 2,596,882. The wrench of U.S. Pat. No. 562,709 appears disadvantageous, however, because the shims are held in place by springs and metal straps which weakens the system, the shims are relatively difficult to operate because they are not thumb operated, the relationship between the open-ended jaw and the handle is simplistic and not of utmost efficiency and one or more of the shims may be moved into the jaw opening without supportive contact against one of the jaws. Likewise, the wrench of U.S. Pat. No. 2,596,882 appears difficult to manufacture and requires shims which are different from each other. Since the shims project beyond the upper jaw in the U.S. Pat. No. 2,596,882 construction, the shims may be deformed under load.
It is, therefore, an object of the present invention to provide an adjustable wrench which alleviates the difficulties concomitant with prior art adjustable wrenches.